The present invention relates to a kit for the detection of microbes using a two step hybridization procedure.
In traditional microbial diagnostics the presence of a microbe in a given sample is demonstrated by isolating the microbe in question. After enrichment cultivations, the microbe is identified either on the basis of its biochemical properties or its immunological properties. Both methods of identification require that the microbe in the sample be viable. Such identification can be laborious and time-consuming. Indeed, the detection of certain viruses, requiring sophisticated biochemical purification or tissue culture techniques, can take as long as 4 to 6 weeks.
The purpose of this invention is to provide a diagnostic kit for detecting the nucleic acid of a microbe in a sample with the aid of a sensitive and specific nucleic acid hybridization technique. The nucleic acid may be of two types, deoxyribonucleic acid (DNA) or ribonucleic acid (RNA).
Nucleic acid hybridization is an old and well known method for investigating the identity of nucleic acids. Hybridization is based on complementary base pairing. When single-stranded nucleic acids are incubated in solution, complementary base sequences pair to form double-stranded stable hybrid molecules. The double-stranded hybrid molecules can be separated from the single-stranded molecules by chemical means.
Some methods based on the identification of nucleic acid(s) have already been applied to microbial diagnostics. Enterotoxigenic Escherichia coli has been identified from fecal samples by colony hybridization using the gene for toxin production as a probe. Positive hybridization has been demonstrated by autoradiography (see Moseley et al., Journal of Infectious Diseases, Vol. 142, pp. 892-898 (1980). Grunstein and Hogness have reported a method for detecting nucleic acids by colony hybridization in Proc. Natl. Acad. Sci. USA, Vol. 72, pp. 3961-3965 (1975). Hybridization has also been used as a method to distinguish between Herpes simplex virus type 1 and 2 after enrichment cultivation (see Brautigam et al., Journal of Clinical Microbiology, Vol. 12, pp. 226-234 (1980). In the latter method, the double-stranded hybrid was separated from the single-stranded nucleic acid by affinity chromatography.
Brandsma and Miller have identified DNA from cells infected with Epstein-Barr virus by hybridizing filters containing immobilized Epstein-Barr virus DNA with a radioactive probe, positive hybridization being detected by autoradiography as described in Proc. Natl. Acad. Sci. USA, Vol. 77, pp. 6851-6855 (1980)).
The present invention utilizes the two step hybridization technique, also called the sandwich hybridization technique, described by Dunn and Hassell in Cell, Vol. 12, pp. 23-36 (1977).